The men taken into custody, David Hernández Cruz and Manuel Alejandro Pérez de Jesús, worked as waiters at the Palace Club, a downtown bar where Mr. Shabazz, 28, was beaten, in what the city prosecutor called a dispute over an excessive bill.

Two other bar employees who the authorities said participated in the beating, which left Mr. Shabazz with fatal skull, jaw and rib fractures, were being sought.

The body of Mr. Shabazz, who for years had wrestled with living in the shadow of his grandfather’s fame, was still at a city morgue on Monday while American consular officials worked to have it returned to the United States. A family spokeswoman said they would have no comment, and no funeral plans have been announced.

Mr. Shabazz arrived in Mexico City from Tijuana, the prosecutor, Rodolfo Fernando Rios Garza, said at a news conference. He went to the bar on Thursday with a man whom friends identified as Miguel Suárez, a Mexican labor activist whom Mr. Shabazz had befriended in the United States and who had been recently deported.

When the argument over the tab broke out around 3 a.m. as they prepared to leave, the two were separated by bar employees, but, for reasons the prosecutor said had not yet been determined, only Mr. Shabazz was beaten. A blunt object was used but no other details were given.

Mr. Shabazz’s companion was taken to another part of the bar and robbed but said he managed to escape and call for help.

The pair disputed a tab that came to around $1,200, Mr. Rios Garza said. Two young women had approached them on the street and invited them to the bar, but although Mexican newspapers have identified the bar as a known brothel, Mr. Rios Garza waved off questions regarding prostitution. Many of the bars in that rundown area charge customers for even a conversation with their female employees, according to Mexican news reports.

Mr. Shabazz consumed several drinks; a prosecutor’s office statement said he had a blood alcohol concentration more than three times the legal limit for driving in most American jurisdictions. But the prosecutor, while not offering details on how much liquor was consumed, said the bill was excessive and was part of the effort to rob Mr. Shabazz and his companion.

He said he found no evidence that race or any motive other than robbery was in play, and there was no indication that the attackers knew Mr. Shabazz came from a famous family.

The investigation, however, has had its stumbles.

There were security cameras in the bar, but after a search of the property two days after the attack, video recording equipment was missing and the cameras were turned toward the walls, the prosecutor’s statement said. It was unclear why the search was delayed, but justice reform advocates have long complained that Mexican investigators do not always move with the speed and forensic acumen of the police in the United States.

The police have interviewed Mr. Suárez, who could not be reached for comment.

Mr. Shabazz was 12 when he set a fire in Yonkers that killed his grandmother, Betty Shabazz. After serving prison time, he walked an erratic path away from his troubled youth.

He had gone to Mexico City with Mr. Suárez with plans to draw media attention to his deportation, Mr. Suárez said on Facebook.